Search results for " Geometry"
showing 10 items of 2294 documents
Surface plasmon routing along right angle bent metal strips
2005
International audience; An efficient routing of surface plasmon polaritons (SPP) is of fundamental importance in the development of SPP-based photonics. This paper reports that microgratings acting as Bragg mirrors can guide SPP along metal stripes waveguides featuring 90 degrees bents. The measurement of the mirrors efficiency, performed by means of photon scanning tunneling microscopy, shows that bent losses as low as 1.9 dB can be achieved. Finally, we demonstrate operating SPP beamsplitters obtained by an appropriate design of the Bragg mirrors constituting elements. (c) 2005 American Institute of Physics.
Fractal geometry and urban patterns – from exploring morphology to applications in planning
2014
International audience; Fractal geometry turned out to be a powerful approach in many domains for describing complex structures which have multiscale properties. In particular, fractal analysis allows making evident scaling properties and hence underlying structural order principles which cannot be discovered by other measuring approaches like densities which refer to one unique scale. We present here how this approach helps to analyze the distribution of build-up surface in urban patterns and how it can be used to link these morphologiocal properties to specific contexts of urbanization. Indeed, contemporary urban patterns have usually an irregular shape reminding rather deposits on surfac…
Fractal geometry for modeling and measuring urban patterns
2012
International audience
The role of virtual work in Levi-Civita's parallel transport
2015
International audience; According to current history of science, Levi-Civita introduced parallel transport solely to give a geometrical interpretation to the covariant derivative of absolute differential calculus. Levi-Civita, however, searched a simple computation of the curvature of a Riemannian manifold, basing on notions of the Italian school of mathematical physics of his time: holonomic constraints, virtual displacements and work, which so have a remarkable, if not dominant, role in the origin of parallel transport.
Building scenarios for a LUTI model : articulation of spaced based models and an agent based model
2013
International audience
Extension des méthodes de géométrie algorithmique aux structures fractales
2013
Defining shapes by iteration allows us to generate new structures with specific properties (roughness,lacunarity), which cannot be achieved with classic modelling.For developing an iterative modeller to design fractals described by a BCIFS, we developed a set oftools and algorithms that permits one to evaluate, to characterize and to analyse different geometricproperties (localisation, convex hull, volume, fractal dimension) of fractals. We identified properties ofstandard CAD operations (intersection, union, offset, . . . ) allowing us to approximate them for fractalsand also to optimize these approximation algorithms.In some cases, it is possible to construct a CIFS with generalised HUTCH…
Development of Removable Visual Impact Indicator or Polymer Composite Materials
2021
The prototype of removable visual impact indicator for thermoset polymer composite materials is developed, and its characteristics are experimentally determined. The indicator is a fabric tape glued by epoxy to the surface of the polymer composite. The tape is impregnated with a composition that provides a visual response at the place of an impact on the composite surface. Ball-drop tests demonstrated the increase of the magnitude of the visual response with the impact energy at different substrate hardnesses. The shelf-life and mode of the tape storage until commissioning are determined. Peel tests showed the ability to remove a used indicator without damaging the surface of the composite.
L'analyse fractale, un nouvel outil pour l'analyse spatiale des agglomérations urbaines
1997
The fractal approach. A new tool for the spatial analysis of urban agglomerations. Fractal geometry is a new approach for the study of spatial distributions. The basic model is a law of hierarchical distribution corresponding to Pareto's law which is familiar to urban geographers and demographers. The methods of fractal analysis can be used to study the spatial organization of human activities across scales. The regularities and the discontinuities in the distributions can then be identified. These discontinuities can be spatially situated. Applying this concept to urbanized areas has shown that districts can be defined and classified according to their scaling relations, thereby allowing d…
Estimation géométrique des tangentes à partir de coniques et algèbre géométrique. Exemples sous GAviewer
2018
National audience; Les nombres complexes sont fortement liés à la géométrie plane. Si les rotations, symétries et similitudes planes parmi d'autres s'expriment aisément à l'aide des complexes, le mérite de ce mode de représentation prend tout son sens dans toutes les compositions de ces transformations. Cette algébrisation des problèmes géométriques est le fil directeur de l'article. Elle fournit ainsi des formules de calcul aisément exploitables sur ordinateur. A titre d'exemple, l'article propose un algorithme géométrique de calcul de tangentes à une conique, son adaptation au contexte de l'algèbre géométrique et son implémentation au moyen d'un logiciel dédié. L'algorithme repose sur le …
Effect of dual blockade of renin-angiotensin system on TGF beta 1 and left ventricular structure and function in hypertensive patients
2007
The effects of 24 weeks losartan and ramipril treatment,both alone and in combination, on left ventricular mass (LVM), circulating transforming growth factor b1(TGFb1), procollagen type I (PIP) and III (PIIIP), havebeen evaluated in hypertensive (HT) patients. A total of 57 HT with stage 1 and 2 essential hypertension were included. After 4 weeks run in, a randomized double blind, three arms, double dummy, independent trial was used. All HT patients were randomly allocated to three treatment arms consisting of losartan (50 mg/daily),ramipril (5 mg/ daily) and combined (losartan 50 mg/daily plus ramipril 5 mg/daily) for 24 weeks. TGFb1, PIP and PIIIP, LVM, LVM/h 2.7 and other echocardiograph…